Mobile robots are becoming increasingly commonplace and are used in such diverse fields as space exploration, lawn mowing and floor cleaning. The last decade has seen particularly rapid advancement in the field of robotic floor cleaning devices, especially vacuum cleaners, the primary objective of which is to navigate an area of a home or office autonomously and unobtrusively whilst cleaning the floor.
A known self-guiding vacuum cleaner is exemplified in EP0803224, which vacuum cleaner includes a chassis supporting a housing with a cover and a front part which is movable with respect to the chassis and forms part of a collision detecting system. To pick up dirt from a floor surface, the vacuum cleaner includes a brush nozzle facing the floor, the brush nozzle leading to an opening in communication with a chamber (16) within which a dirt container is stored, the dirt container here being in the form of a bag. Dirt is separated from the air by the pores of the bag when air flows out of the bag, after which air flows into the body of the machine, past a motor and fan unit and through a set of outlet openings to the atmosphere. It will be appreciated that such a means of separating dirt and dust from an airflow suffers from the usual problems that the pores of the dirt container can block, which reduces the efficiency of the vacuum cleaning function of the appliance.
Other autonomous vacuum cleaners are known which function primarily as floor sweepers although they also have a small vacuum function to control dust generation from the machine.
Another example of an autonomous vacuum cleaner is described in WO00/36968. Here, a robotic unit comprises a chassis to which is mounted a cleaner head having a suction opening and a rotatably driven brush bar. The chassis also includes a motor and fan unit which is configured to draw dirty air into the vacuum cleaner via the suction opening in the cleaner head. A cyclonic separator is carried on the chassis and dirty airflow is ducted into the cyclonic separator from the cleaner head. Once the dirty air has been cleaner by the cyclonic separator, the exiting air is conducted past the motor and fan unit so that the motor can be cooled before the air is expelled from the machine to atmosphere. Optionally, a motor can be incorporated at a downstream position of the motor and fan unit in order to filter fine contaminants that may not have been stripped from the air flow by the cyclonic separator. Although a robotic vacuum cleaner equipped with a cyclonic separation as described above avoids the need for traditional bags and filters, the cyclonic separation system must operate with a very high degree of efficiency, which is difficult to achieve in a small space envelope inherent in robotic vacuum cleaners.
It is with a view to improving the separation efficiency of robotic vacuum cleaners that the present invention has been devised.